**URL**: https://todo-lux.com/en/blog/cri-iluminacion-que-mide-limites-especificacion-profesional **Locale**: en **Title**: CRI in lighting: limits, R9 and TM-30 explained - Todolux --- CRI in Lighting: What It Measures, Its Limits and How to Specify It Professionally ==================================================================================== ![Todolux Lighting](https://todo-lux.com/storage/profile-photos/JgWPA04yGViTT8ASzCk8RLf9VHG2QQvosNpr9ooy.png)Todolux Lighting Lighting designer Publication date 18 de June, 2026 Reading time 19 mins read ![CRI in Lighting: What It Measures, Its Limits and How to Specify It Professionally](https://todo-lux.com/storage/6882/conversions/01KVA4CG6YWWRRMGNC7D4V4FYP-blog-card.webp?v=1784218005) Professional guide to CRI/Ra in lighting: what it measures, its limits, why R9 matters and when TM-30 helps specify color rendition more accurately. --- **Direct answer:** CRI in lighting indicates the average fidelity with which a light source reproduces selected colors compared with a reference source of the same correlated color temperature. It is useful for comparing luminaires, but it does not measure total light quality and it does not guarantee accurate rendering of every color. Professional specifications should read CRI together with R9, SDCM color consistency, glare control, flicker, luminous efficacy and, when color is critical, fuller color rendition metrics such as TM-30. The goal is not to demand the highest value in every project, but to specify the right color performance for the application. Technical summary ----------------- - **CRI/Ra measures average fidelity, not total quality:** it does not evaluate visual comfort, flicker, UGR, efficiency or luminaire-to-luminaire consistency. - **Ra is limited:** it is calculated from 8 moderately saturated color samples and does not include saturated colors such as deep red. - **R9 matters:** it helps detect whether a luminaire renders skin, food, wood, textiles and warm tones correctly. - **TM-30 adds diagnostic value:** it combines fidelity (Rf), gamut or saturation (Rg) and color vector analysis. - **Specification must be contextual:** offices, fashion retail, healthcare and galleries do not need the same color-rendering requirements. Brief definitions ----------------- Use this table as a quick glossary: first identify what each metric measures, then check the interpretation trap to avoid. Table 1. Color metrics commonly found in lighting datasheetsMetricUseful readingWatch out for...**CRI / Ra**Average color fidelity across 8 standard samples.It does not equal total luminaire quality.**R9**Deep red rendering: skin, food, wood, textiles and warm tones.It is not included in the Ra average; request it separately.**TM-30 Rf**Color fidelity with a broader sample set.It does not express visual preference or design intent on its own.**TM-30 Rg**Average tendency to saturate or desaturate colors.A value above 100 is not automatically “better”.**SDCM**Color consistency between luminaires or production batches.It does not measure object color rendering.What CRI Measures in Lighting ----------------------------- CRI, or Color Rendering Index, measures a light source's ability to reproduce colors compared with a reference source of the same correlated color temperature (CCT). In datasheets, “CRI 80”, “CRI 90” or “CRI > 95” usually refers to the Ra value. The classic CRI/Ra method is defined in [CIE 13.3-1995: Method of Measuring and Specifying Colour Rendering Properties of Light Sources](https://cie.co.at/publications/method-measuring-and-specifying-colour-rendering-properties-light-sources). It compares the tested light source with a reference illuminant and calculates color shifts across standardized samples. CRI answers one specific question: how accurately does this light source reproduce selected colors compared with its physical reference? It does not answer whether the luminaire is comfortable, efficient, stable, flicker-free or suitable for every visual task. How CRI/Ra is Calculated ------------------------ 1. The spectrum of the tested light source is measured. 2. It is compared with a reference source of the same CCT. 3. Eight standard color samples (R1 to R8) are evaluated. 4. The arithmetic mean of those eight values becomes Ra. That is why a high CRI/Ra value indicates strong average fidelity for those samples, but not necessarily excellent rendering of saturated colors, deep reds, skin tones or warm materials. Why Classic CRI is Limited with LED Technology ---------------------------------------------- CRI remains useful, but it has clear limitations for modern LED sources. Many white LEDs combine a blue chip with phosphors that convert part of that energy into other wavelengths. The result may be efficient and visually acceptable without being continuous or balanced across the visible spectrum. The limitations of classic CRI and the need for more robust fidelity metrics are addressed by [CIE 224:2017: Colour Fidelity Index for Accurate Scientific Use](https://cie.co.at/publications/colour-fidelity-index-accurate-scientific-use). A luminaire can perform well on R1-R8 and still fail in spectral regions that matter for saturated colors. The table below shows when each metric is useful without treating any of them as a universal replacement for the others. Table 2. CRI/Ra, R9 and TM-30: practical uses and limitsMetricUse it for...Do not use it for...**CRI / Ra**Fast comparison of average fidelity in datasheets.Evaluating deep reds, saturation or color-shift direction.**R9**Controlling deep red in skin, food, wood, leather and textiles.Summarizing the whole visible spectrum.**TM-30 Rf**More robust LED fidelity analysis in demanding projects.Deciding visual intent without Rg and the vector graphic.**TM-30 Rg**Understanding whether a source saturates or dulls colors.Concluding that more saturation is always better.What R9 is and Why it Matters ----------------------------- R9 is a special CRI index that evaluates deep red rendering. It is important because it is not part of the Ra average. A luminaire can claim Ra ≥ 90 while having a low, near-zero or even negative R9 value. - **Skin and human tissue:** low R9 can make faces appear pale or unhealthy. - **Food retail:** meat, fruit and fresh produce lose perceived freshness when deep red is weak. - **Fashion and interiors:** textiles, leather, wood and warm finishes can appear washed out. - **Healthcare and beauty:** visual assessment often requires tighter color control. **Practical rule:** when color affects perception, sales or diagnosis, do not specify only Ra ≥ 90. Add an R9 threshold, such as R9 ≥ 50 for demanding projects and R9 ≥ 80 for critical applications. TM-30: A Fuller Reading of Color Rendition ------------------------------------------ [ANSI/IES TM-30-24: IES Method for Evaluating Light Source Color Rendition](https://store.ies.org/product/technical-memorandum-ies-method-for-evaluating-light-source-color-rendition/) is a color evaluation method designed to describe modern light sources more completely. It should not be treated as an automatic replacement for CRI in every project, but as a stronger diagnostic tool when color rendition has technical, commercial or regulatory importance. ### Rf: Fidelity Index Rf measures color fidelity on a 0 to 100 scale. It is conceptually similar to Ra but calculated from more samples. ### Rg: Gamut Index Rg indicates whether the source tends to desaturate or saturate colors compared with the reference. ### Color Vector Graphic The color vector graphic shows where a source shifts, saturates or desaturates colors around the hue circle. This is useful in retail, museums, hospitality, food and other applications where hue matters. The IES technical position explains why TM-30 gives a more complete reading than CRI/Ra for modern color rendition: [IES Position Statement PS-11-18 on TM-30](https://ies.org/advocacy/ps-11-18/). How to Specify CRI, R9 and TM-30 by Application ----------------------------------------------- Not every space needs the same color-rendering level. [UNE-EN 12464-1:2022: Luz e iluminación. Iluminación de los lugares de trabajo. Parte 1: Lugares de trabajo en interiores](https://tienda.aenor.com/p/norma-une-en-12464-1-2022-n0068596) relates indoor workplace lighting criteria to visual performance, comfort and task suitability. In practice, color must be balanced with glare, uniformity, efficiency and maintenance. For project use, the table separates two things: indicative values and the real design priority. Table 3. Color-rendering specification recommendations by applicationApplicationIndicative valuesProfessional priority**Offices, classrooms and standard work areas**Ra ≥ 80 R9 not critical unless color tasks exist TM-30 optionalPrioritize UGR, comfort, flicker-free operation, uniformity and efficiency.**Fashion and textile retail**Ra ≥ 90 R9 ≥ 50 High Rf and controlled RgAvoid color shifts that distort product appearance.**Food and fresh produce**Ra ≥ 90 R9 ≥ 70 TM-30 recommendedUse appropriate spectra without falsifying perceived freshness.**Hotels, restaurants and premium residential**Ra ≥ 90 R9 ≥ 50 TM-30 useful when ambience is criticalBalance warmth, comfort, skin tones and decorative materials.**Museums, galleries and heritage**Ra ≥ 95 R9 ≥ 80 TM-30 strongly recommendedControl fidelity, radiation impact, CCT, SDCM and conservation criteria.**Healthcare, beauty and visual diagnosis**Ra ≥ 90 R9 ≥ 80 depending on task TM-30 recommendedEnsure reliable rendering of skin and tissue when it affects clinical perception.Recommended Professional Criterion ---------------------------------- Use the values above as indicative specification criteria, not as universal regulatory requirements. The final decision should be adjusted to the visual task, applicable standard, product type, energy budget and color-risk level of the project. **In one sentence:** specify CRI/Ra as a minimum requirement, add R9 when warm tones or skin are involved, and use TM-30 when color is a design, sales or diagnostic variable. Common CRI Interpretation Errors -------------------------------- - **“CRI 90 guarantees good rendering of every color”.** No. It indicates a high Ra average, not necessarily strong R9 or saturated-color performance. - **“The higher the CRI, the better in every case”.** Not always. Higher fidelity may reduce efficacy, increase cost or be unnecessary for the task. - **“TM-30 always replaces CRI”.** No. TM-30 expands the analysis, but CRI/Ra remains common for quick comparison and minimum requirements. - **“SDCM and CRI measure the same thing”.** No. SDCM measures consistency between luminaires; CRI measures object color rendering. Professional Specification Checklist ------------------------------------ - Define the visual task and the real color-rendering requirement. - Request Ra and R9 when color matters. - Use TM-30 (Rf, Rg and vector graphic) for retail, museums, food, healthcare or high-demand projects. - Control SDCM to avoid visible differences between luminaires. - Do not sacrifice efficiency, UGR, maintenance or comfort by demanding maximum CRI without justification. FAQ on CRI in Lighting ---------------------- ### Are CRI and Ra the same? In commercial use they are often treated as equivalent, but technically CRI is the overall method and Ra is the average index calculated from the first eight color samples. ### Does CRI 90 mean good light quality? It means good average fidelity according to Ra, not total light quality. A luminaire should also be assessed for R9, CCT, SDCM, flicker, UGR, efficiency, optics and task suitability. ### When should R9 be required? When skin, food, textiles, wood, leather, fresh produce, beauty, healthcare or warm tones influence visual perception. ### Does TM-30 replace CRI? Not universally. TM-30 gives a fuller reading and is recommended for critical projects, while CRI/Ra remains a common metric for quick comparison and minimum requirements. ### Why can very high CRI reduce efficiency? Because broader color rendering often requires phosphors or spectral mixes that cover more of the visible spectrum but reduce luminous efficacy in lumens per watt. ### How are CRI and SDCM related? They are different metrics. CRI describes how a source renders colors; SDCM describes apparent color variation between units or batches. Technical references -------------------- - [CIE 13.3-1995: Method of Measuring and Specifying Colour Rendering Properties of Light Sources](https://cie.co.at/publications/method-measuring-and-specifying-colour-rendering-properties-light-sources) - [CIE 224:2017: Colour Fidelity Index for Accurate Scientific Use](https://cie.co.at/publications/colour-fidelity-index-accurate-scientific-use) - [ANSI/IES TM-30-24: IES Method for Evaluating Light Source Color Rendition](https://store.ies.org/product/technical-memorandum-ies-method-for-evaluating-light-source-color-rendition/) - [IES Position Statement PS-11-18 on TM-30](https://ies.org/advocacy/ps-11-18/) - [UNE-EN 12464-1:2022: Luz e iluminación. Iluminación de los lugares de trabajo. Parte 1: Lugares de trabajo en interiores](https://tienda.aenor.com/p/norma-une-en-12464-1-2022-n0068596) [ CRI ](https://todo-lux.com/en/blog/tag/cri) [ R9 ](https://todo-lux.com/en/blog/tag/r9) [ TM-30 ](https://todo-lux.com/en/blog/tag/tm-30) [ Color Quality ](https://todo-lux.com/en/blog/tag/calidad-cromatica) [ Color Rendering ](https://todo-lux.com/en/blog/tag/reproduccion-color) [ SDCM ](https://todo-lux.com/en/blog/tag/sdcm) Community Comments -------- Share questions or thoughts about this article. Comments are reviewed before publication. Your comment Write your comment... Register to comment There are no approved comments yet. ### Centralize your lighting searches Find the best solution for your project in just a few clicks with Todolux. - ✓ Download technical files - ✓ Create your own project - ✓ Find equivalents easily CREATE FREE ACCOUNT ![]()